ISTANBUL — Turkish investigators were permitted to search Saudi Arabia’s consulate on Monday, 13 days after journalist Jamal Khashoggi vanished while visiting the mission, as President Trump dispatched Secretary of State Mike Pompeo to discuss the case with King Salman, the Saudi ruler.

As pressure mounted on Saudi Arabia to disclose what it knows about Khashoggi’s fate, U.S. officials began predicting over the weekend that the Saudis would inevitably admit complicity in the death of Khashoggi and claim a “botched operation,” said one person familiar with the discussions.

Over the past few days, Saudi officials have discussed issuing a statement that, in part, would mention a botched operation and call for the punishment of culpable officials, according to another person with knowledge of the discussions. The statement would be issued only after Saudi Arabia reached an agreement with Turkey on how to proceed with the investigation, the person said.

Speaking to reporters, Trump said Monday that he had talked for about 20 minutes with the king and that Salman had firmly denied the kingdom’s involvement in Khashoggi’s disappearance.

“I don’t want to get into his mind, but it sounded to me like maybe these could have been rogue killers,” Trump added. “Who knows? We’re going to try getting to the bottom of it very soon, but his was a flat denial.”

It was not clear whether Trump’s mention of “rogue killers” was his own speculation, a theory he had heard from the king or an intended confirmation that Khashoggi was killed in the consulate, as Turkish investigators have concluded.

Saudi Arabia has strenuously denied any knowledge of Khashoggi’s whereabouts, saying — without providing evidence — that he walked out of the consulate soon after entering Oct. 2.

Trump said Pompeo has license to travel wherever necessary, including Turkey, to investigate what happened. The president first announced Pompeo’s trip in a tweet in which he said that Saudi Arabia is “working closely with Turkey to find answer.”

Trump said he stressed the importance of the case to Salman. “The world is watching. The world is talking. And this is very important to get to the bottom of it. And I think he understands that very well,” Trump said. “He did say, very strongly, that he’s dealing with Turkey; that they’ve come to an agreement, that they’re investigating it together. And I think that’s a good thing.”

Khashoggi’s family issued a statement Monday urging an “independent and impartial international commission” to look into his disappearance.

“We are sadly and anxiously following the conflicting news regarding the fate of our father after losing contact with him two weeks ago, when he disappeared after entering the Saudi consulate in Istanbul. Our family is traumatized, and yearns to be together during this painful time. The strong moral and legal responsibility which our father instilled in us obliges us to call for the establishment of an independent and impartial international commission to inquire into the circumstances of his death. We are grateful to all those who have respected our privacy during these difficult times,” the statement said.

Trump’s comments came hours before a team of Turkish investigators arrived at the Istanbul consulate to conduct a search of the premises with Saudi Arabia’s cooperation. Turkish officials had complained publicly in recent days that the Saudis were refusing to allow a search of the property.

An agreement allowing the inspection came after Salman called Turkish President Recep Tayyip Erdogan on Sunday. Salman thanked him for welcoming the kingdom’s proposal to set up a “joint working group” to probe Khashoggi’s disappearance, a Saudi statement said.

But hours before the Turkish forensic team arrived, journalists photographed a cleaning crew entering the consulate, hauling buckets, mops and what appeared to be bottles of cleaning solution. When the Turkish investigators entered the consulate, some wearing white protective gear, they “smelled chemicals had been used,” according to two officials in contact with the investigators.

“They are trying to make fun of us and our willingness to cooperate,” one of the officials said.

Khashoggi lived in self-imposed exile in the United States for the past year and wrote columns in The Washington Post criticizing the Saudi leadership. He visited the consulate Oct. 2 to obtain documents related to his upcoming wedding, but he was never seen leaving.

The Saudi government has faced intense pressure to reveal his fate. Turkish officials have released details of their investigation, including video that suggests a team of Saudi agents was dispatched to Istanbul to either capture Khashoggi or kill him.

The Turkish government has also told the Trump administration that it has audio and video recordings of what occurred inside the consulate that day. U.S. officials have said this material supports the conclusion that Khashoggi was interrogated, tortured and then killed.

U.S. officials have also said that the crown prince of Saudi Arabia, Mohammed bin Salman, ordered an operation to lure Khashoggi from his home in Virginia back to Saudi Arabia and detain him, according to U.S. intelligence intercepts of Saudi officials discussing the plot.

Trump has warned that Saudi Arabia would face “severe punishment” if it were found to have killed Khashoggi. And on Sunday, Britain, France and Germany released a joint statement expressing “grave concern” about the case and calling for a “credible investigation.”

A defiant Saudi statement Sunday said the kingdom rejected any “threats and attempts to undermine it, whether by threatening to impose economic sanctions, using political pressures, or repeating false accusations.”

Democrats in Congress ridiculed the theory, floated by Trump, that “rogue killers” had slain Khashoggi.

“Been hearing the ridiculous ‘rogue killers’ theory was where the Saudis would go with this,” Sen. Chris Murphy (D-Conn.), a member of the Senate Foreign Relations Committee, said in a tweet. “Absolutely extraordinary they were able to enlist the President of the United States as their PR agent to float it.”

As part of a growing international backlash against the Saudi government, an increasing number of prominent business leaders and companies have said they will no longer attend a major investment conference scheduled to be held in Saudi Arabia this month. Several high-profile finance executives have withdrawn, including the heads of JPMorgan Chase and the asset management giants BlackRock and Blackstone Group. Their action came after tech and media executives said they would not participate.

On Monday, two more Washington lobbying firms dropped their representation of Saudi Arabia amid the escalating uproar over Khashoggi’s disappearance, according to people familiar with the decisions.

The Glover Park Group notified the Saudi Embassy in Washington that it was canceling its two-year-old contract to represent the kingdom, according to a person with knowledge of the move. The consulting firm, which was established in 2001 by Democratic political veterans, had been receiving a fee of $150,000 a month to help the Saudis with a range of government relations issues, according to disclosure reports filed with the Justice Department.

Separately, the GOP-founded lobbying powerhouse BGR Group, which had an $80,000-a-month contract with the Saudi government, announced that it was also dropping the kingdom as a client.

“BGR is no longer working for Saudi Arabia,” said Jeffrey H. Birnbaum, president of BGR’s public relations division.

In all, three major Washington lobbying firms have severed ties with Saudi Arabia in the wake of the reports that Khashoggi was killed. Late last week, the Harbour Group announced that it was terminating its relationship with the kingdom.

The defections underscore the depth of the crisis facing Saudi Arabia, which plowed $27 million into lobbying in Washington last year, making it one of the highest-spending countries seeking to influence U.S. policy, according to public records.

On Monday, the Saudi Embassy canceled a long-planned reception that was to be held Thursday evening honoring the country’s annual National Day, which commemorates the renaming of the kingdom in 1932.

Invited guests received a short email Monday morning informing them that the event was off.

“Please be advised that the reception for the National Day of the Kingdom of Saudi Arabia on Thursday, October 18, from 6:00 pm-8:00 pm has been canceled,” said the email, according to a copy obtained by The Washington Post. It did not explain the reason for the change in plans.

The reception would have been part of a weeks-long celebration. An embassy spokesman did not immediately respond to a request for comment.

Wagner reported from Washington. Erin Cunningham, Zeynep Karatas and Loveday Morris in Istanbul and Tom Hamburger, John Hudson and Jeanne Whalen in Washington contributed to this report.